PROGRESSION (not ordered according to difficulty, no spoilers) [DOCS for more info: DUNGEONS / RIFTS]:
[REQ <59] Level Challenge: Throne of Destruction -> last wave portal -> Tran Athulua (kill under level 59 or pay extra AC).
[REQ 80] Ennead Challenge: Nightmare Mephisto -> K3BA portal
[TOKENS] Veterans (nightmare): A1 jail / A2 Canyon / A3 Travnical / A4 City-River / A5 WSK -> cube all with Class Charm
[REQ 105] The Butcher: A1 Stony Field -> Tristram -> inside house [LOCK:20s]
[REQ 105] Infernal Machine: A1 Tamoe Highland -> The Pit
[REQ 105] Island of the Sunless Sea: A2 Stony Tomb 1 -> Treasure Vault -> Kill Gheed's Mentor
[REQ 105] Death Projector: A3 Flayer Jungle -> Swampy Pit -> Proving Grounds [LOCK:30s]
EXP->110: IotSS / A5 Red portals / End of A5 / A5 Icy Cellar
[REQ 110] Tal Rasha: A2 Canyon of the Magi -> Tal Rasha Tomb -> Kill guardians of duriel chamber entrance
[REQ 110] Creature of Flame: A3 Lower Kurast -> kill The Vizier at the entrance -> Caldeum -> Dimensional Sanctum [LOCK:20s]
[REQ 110] Jitan: A3 Town -> Torajan Jungles -> north-west
[REQ 110] Akarat: A3 Town -> Torajan Jungles -> north
[REQ 110] King Koth: A5 Ancient's Way -> Mount arreat -> kill a guy that opens portal [LOCK:120s]
EXP->115: Torajan Jungles / Cow Level
[REQ 115] Black Road Challenge: A1 Town (Warriv) -> Bramwell -> Church of Dien-Ap-Sten
[REQ 115] Bull Prince Rodeo: A1 Catacombs 4 (Wirt's Leg in Andariel's room) -> Cow level (kill king) -> Another leg -> rodeo portal
[REQ 115] Tran Athulua: A2 Halls of the Dead level 3 -> kill Kethryes at golden chest
[REQ 115] Kurast 3000 BA: A3 Town -> Torajan Jungles -> north
[REQ 115] Legacy Of Blood: A3 Town -> Torajan Jungles -> south-east [LOCK:30s]
[REQ 115] Rathma Square: A3 Lower Kurast -> kill The Vizier at the entrance -> Caldeum -> Rathma Square
[REQ 115] Khalimgrad: A4 Plains of Despair -> Izual -> Diamond Gates -> Silver City -> Library Of Fate (Khalimgrad)
[REQ 115] Cathedral of Vanity: A4 Plains of Despair -> Izual -> Diamond Gates -> Silver City -> Library Of Fate [LOCK:30s]
[REQ 115] Azmodan: A4 Chaos Sanctuary -> kill Ghom to obtain Key of Sin
EXP->120: K3BA / Tran Athulua / Khalimgrad / Azmodan level
[REQ 120] Duncraig: A1 Town (Warriv) -> Bramwell -> Subterranean Corridor
[REQ 120] Kabraxis: A1 Town (Warriv) -> Bramwell -> Church of Dien-Ap-Sten (boss opens portal)
[REQ 120] Teganze: A3 Town -> Torajan Jungles -> north-east -> Torajan Cemetery
[REQ 120] Triune: A3 Lower Kurast -> kill The Vizier at the entrance -> Caldeum -> Rathma Square (kill boss)
[REQ 120] Athulua: A2 Halls of the Dead level 3 -> Tran Athulua -> Island of Skartara (summon at the center, scroll can drop in TA)
[REQ 120] Quov Tsin: A3 Lower Kurast -> kill The Vizier at the entrance -> Caldeum -> Vizjerei Temple
[REQ 120] Ureh: A3 Lower Kurast -> kill The Vizier at gate -> Caldeum -> Vizjerei Temple -> Ureh (path from cabin to banner)
[REQ 120] Judgment Day: A4 Plains of Despair -> Izual -> Diamond Gates -> Silver City -> Silver Spire 1->2 -> Crystal Arch
EXP->125: Duncraig / Teganze / Triune
[REQ 125] Xazax: A2 Halls of the Dead level 3 -> Tran Athulua -> Island of Skartara -> Wretched Sands (hug left side)
[REQ 125] Toraja: A3 Town -> Torajan Jungles -> north-east -> Torajan Cemetery
[REQ 125] Vizjun: A3 Flayer Jungle -> Swampy Pit -> Proving Grounds
[REQ 125] Yshari Sanctum: A3 Lower Kurast -> kill The Vizier at the entrance -> Caldeum
[REQ 125] Astrogha: A3 Town -> Torajan Jungles -> north-west [LOCK:300s]
[REQ 125] Zorun Tzin: A3 Town -> Torajan Jungles -> north-east -> Torajan Cemetery -> Teganze -> Mbwiru Eikura
[REQ 125] Startled Witch: A3 Lower Kurast -> kill The Vizier at gate -> Caldeum -> Vizjerei Temple -> Ureh north [LOCK:60s]
[REQ 125] Belial: A4 Chaos Sanctuary -> kill Maghda to obtain Key of Lies [LOCK:60s]
[REQ 125] Fauztinville: A5 Open portal using Black Road charm upgraded with Kabraxis Stones
[REQ 125] Bremmtown: A5 Fauztiville north-east
EXP->∞: Fauztinville / Bremmtown / Vizjun / Toraja / Duncraig
[REQ 130] Brother Laz: A3 Flayer Jungle -> Swampy Pit -> Proving Grounds -> Vizjun (north-east) -> Genesis [LOCK:15s]
[REQ 130] Uldyssian: A4 Plains of Despair -> Izual -> Diamond Gates -> Silver City -> Silver Spire 1->2 -> Crystal Arch
[REQ 130] The Void: A4 -> Izual -> Diamond Gates -> Silver City -> Library Of Fate -> CoV -> Black Abyss [LOCK:1500s]
[REQ 135] Samael: Farm hell Baal that drops mystery item with clues. [LOCK:1200s]